Diode laser-induced thermal damage evaluation on the retina with a liposome dye system

Background and Objectives: The aim of the study was to evaluate the feasibi lity of retinal thermal damage assessment in a rabbit eye model by using la ser-induced release of liposome-encapsulated dye. Study Design/Materials and Methods: After anesthesia, thermosensitive lipos omes (DiStearoyl Phosphatidyl Choline: DSPC) loaded with 5,6-carboxyfluores cein were injected intravenously to pigmented rabbits. Retinal photocoagula tions were performed with a 810nm diode laser (P=100-400 mW, empty set = 50 0 mu m, 1s) (OcuLight(R), IRIS Medical Instruments, Mountain View, CA). Flu orescence measurements in the area of the laser exposures were then realize d with a digitized angiograph (CF-60UVi(R), Canon-Europe, The Netherlands; OcuLab(R), Life Science Resources,(R) UK). Results: Fluorescent spots were observed for power ranging from 100 +/- 5 m W to 400 +/- 5 mW. The fluorescence intensity increased linearly with the p ower and reached a plateau at 280 +/- 5 mW. The fluorescence intensity was correlated to the maximum temperature at the center of the laser spot with a linear increase from 42 +/- 3 degrees C to 65 +/- 3 degrees C. These resu lts are in agreement with our two previous studies with DSPC liposomes for temperature measurements in a tissue model and then in a vascular model. Conclusion: This preliminary study demonstrates the possibility of a laser- induced release of liposome-encapsulated dye for a quantification of diode laser induced thermal damage in ophthalmology. Such a method could be usefu l for a real-time monitoring of laser photocoagulation for conditions such as choroidal neovascular membranes when a precise thermal damage is require d near the foveolar area. Lasers Surg. Med. 24:61-68, 1999. (C) 1999 Wiley- Liss, Inc.